Fix alias varpool node streaming

[Jan Hubicka]

> On Wed, May 5, 2010 at 2:04 PM, Jan Hubicka <hubicka@ucw.cz> wrote:
> > Hi,
> > I missed the following failure compiling gcc.c-torture/compile/20040323-1.c
> > caused by previous patch. Â The problem here is that varpool has two kinds of
> > aliases. Â One kind if created via varpool_extra_name_alias interface that sits
> > off the main list of varpool nodes, other kind is created by
> > assemble_alias_pair.
> >
> > I have patch to clean this up, but it is more involved and thus I am testing
> > the following patch fixing the ice that makes streamer happy about this fact.
> > Will commit it once testing finish. Â I apologize for the breakage.
> 
> We indeed should get rid of the alias_pair stuff and use
> same-body and varpool aliases.

That is what I am shooting for, but there are some side cases. 
(i.e. assemble aliases visibility differs, while same-body does not)

I am thinking now to really replace all this by a symbol table.  I.e
make symbol_node structure that is inherited by cgraph_node/varpool_node and
alias_node and try to get these correct.  But its bigger project.

Honza